Fix "do not show" for tab closing

When this setting was split up from another one, one place was forgotten.

src/gui/PreviewWindow.cc

@@ -296,7 +296,7 @@ void PreviewWindow::closeEvent(QCloseEvent *event)
 		}
 	}
 	if (has_unsaved_changes &&
-	    getSetting("user::warnings::warn_unsaved_ini", "value") == "TRUE") { //at least one tab has unsaved changes
+		getSetting("user::warnings::warn_unsaved_preview", "value") == "TRUE") { //at least one tab has unsaved changes
 		const int cancel = warnOnUnsavedIni();
 		if (cancel == QMessageBox::Cancel) {
 			event->ignore();